1. Field of the Invention
The present invention relates to a current sensor for detecting a current flowing through an electric circuit mounted to equipment such as an automobile and an electric circuit using this current sensor, and more particularly, to a technique for enhancing a detection precision of a current.
2. Description of Related Art
There is a conventionally known current sensor for detecting a current flowing through an electric circuit mounted in, e.g., an automobile using a Hall element which is one of magnetic-electric power converting element. One example of such current sensors is disclosed as xe2x80x9cLarge current detecting apparatusxe2x80x9d in Japanese Patent Application Laid-open No. H6-174753.
As shown in FIG. 1, this large current detecting apparatus comprises a busbar 70, and a magnetic flux detector 71 as a magnetic-force collecting core wound around the busbar 70. The magnetic flux detector 71 comprises a flexible bag-like body having ferrite powder therein, and may be formed into an arbitrary shape.
A Hall element 73 is provided in a gap 72 formed between both ends of the magnetic flux detector 71, thereby generating, in the Hall element 73, a voltage proportional to a magnetic flux generated by a current flowing through the busbar 70. Based on this voltage, a value of the current flowing through the busbar 70 is displayed on a display unit 74.
According to this conventional large current detecting apparatus, if a positional relation of three parts, i.e., the gap formed between the both ends of the magnetic flux detector, the Hall element and a conductor is not set precisely, the current detecting precision is lowered.
However, in the case of the current detecting apparatus comprising such parts assembled therein, mounting positions of the conductor, the magnetic flux detector and the Hall elements are slightly varied in some cases and therefore, there is a problem that it is difficult to precisely set the positional relation of the above parts and thus, the current detecting precision is lowered.
The present invention has been achieved to solve the problem of such a conventional current detecting apparatus, and it is an object of the invention to provided a current sensor which is capable of enhancing the current detecting precision and which can be assembled excellently. Another object of the invention is to provide an electric circuit using the above current sensor.
To achieve the above object, according to a first aspect, there is provided a current sensor comprising a cabinet, a sensor conductor partially accommodated in the cabinet and secured to the cabinet and having opposite ends pulled out from the cabinet, and a magnetic-electric power converting element accommodated in the cabinet and secured to the cabinet, and disposed in the vicinity of the sensor conductor.
With the current sensor of the first aspect, both the sensor conductor and the magnetic-electric power converting element are secured to the cabinet and integrally formed together. Therefore, since the positional relation between the magnetic-electric power converting element and the sensor conductor through which a current to be measured flows is precisely determined, it is possible to enhance the detecting precision of a current. Further, since this current sensor does not have a magnetic-force collecting core, the current sensor can be made smaller, and is suitable for detecting a large current. Further, since the current sensor itself can be handled as one part, it is easy to handle the sensor.
According to a second aspect of the invention, the current sensor further comprises a ring-like magnetic-force collecting core secured to the cabinet such that the magnetic-electric power converting element is located in a gap.
With the current sensor of the second aspect, since most of the magnetic flux generated by a current flowing through the sensor conductor is converged by the ring-like magnetic-force collecting core and supplied to the magnetic-electric power converting element, it is possible to detect a small current flowing through the sensor conductor with high precision.
According to a third aspect of the invention, the current sensor further comprises square magnetic-force collecting cores respectively disposed on the cabinet in front of and behind the magnetic-force sensing faces of the magnetic-electric power converting element.
With the current sensor of the third aspect, since the bulk of the magnetic flux generated by a current flowing through the sensor conductor is converged by the square magnetic-force collecting cores and supplied to the magnetic-electric power converting element, it is possible to detect a small or medium current flowing through the sensor conductor with high precision. Further, since the square magnetic-force collecting cores are respectively disposed in front of and behind the magnetic-force sensing faces of the magnetic-electric power converting element, the current sensor can be formed smaller as compared with that of the second aspect.
According to a fourth aspect of the invention, each of opposite ends of the sensor conductor is formed such as to have compatibility with an end of a fuse.
With the current sensor of the fourth aspect, the fuse can be removed and the current sensor can be mounted. Therefore, since it is possible to detect a current flowing through the fuse, it is possible to monitor a state of a load connected through the fuse.
According to a fifth aspect of the invention, the current sensor further comprises a display unit for displaying information corresponding to an electric signal from the magnetic-electric power converting element.
With the current sensor of the fifth aspect, since it is possible to visually check a value of current flowing through the sensor conductor of the current sensor, it is possible to easily examine electric circuits in an assembling line of automobiles and inspect vehicles.
According to a sixth aspect of the invention, there is provided an electric circuit comprising a current sensor including a cabinet, a sensor conductor partially accommodated in the cabinet and secured to the cabinet and having opposite ends pulled out from the cabinet, and a magnetic-electric power converting element accommodated in the cabinet and secured to the cabinet, and disposed in the vicinity of the sensor conductor, and a wire conductor used for wiring of the electric circuit and having fitting portions to be fitted to terminals of the sensor conductor of the current sensor.
With the electric circuit of the sixth aspect, since the current sensor can be mounted only by fitting the terminals of the current sensor to the connecting portions formed on the wire conductor, the mounting operation can be carried out easily.
According to a seventh aspect of the invention, in the electric circuit of the sixth aspect, the wire conductor have branch path formed with fitting portions, the terminals of the sensor conductor of the current sensor are fitted to the fitting portions formed on the branch path.
With the electric circuit of the seventh aspect, since a branch current flowing through the branch path is smaller than a current flowing through the entire wire conductor, it is possible to detect a large current using the magnetic-electric power converting element having a low saturation point.